US5065098A
Expired / Lapsed
US
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System for locating concealed underground objects using digital filtering
Assignee: Charles Machine Works Inc
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Filing: 1990-06-18
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Granted: 1991-11-12
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Expires: 2010-06-18
Abstract
Abstract A locating system has its performance enhanced by the use of digital filtering. The locating system may include a transmitter for transmitting an electromagnetic signal from a concealed object. The locating system may also use electromagnetic signals from existing electromagnetic sources unrelated to the locator system. A receiver is provided for receiving a selected electromagnetic signal. The signal is subsequently converted from an analog signal into a digital signal and subjected to digital filtering. The resulting digital signal is then processed to provide location information about the concealed object.
Inventors
- 👤 Lloyd N. Salsman
- 👤 Leslie D. Hoy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 09:01
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/15
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
178 words
A system for locating a concealed object comprising: transmitting means for transmitting an electromagnetic signal from said concealed object; and receiving and processing means for receiving and processing said electromagnetic signal, said receiving and processing means including antenna means for receiving said electromagnetic signal as an analog signal; amplifying means for amplifying said received analog signal; analog-to-digital converter means for converting said amplified analog signal to a digital signal, said analog-to-digital converter means sampling said amplified analog signal at a predetermined frequency; digital filter means for filtering said digital signal, said digital filter means including a two-stage digital filter, the filter characteristics of said first stage of said two-stage digital filter being defined by parameters AO11 and AO12, and the filter characteristics of said second stage of said two-stage digital filter being defined by parameters AO21 and AO22, wherein AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768, wherein q=quality factor, fctr=center frequency, fsmpl=sampling frequency, and x=1 or 2; and processing means for processing said filtered digital signal to provide an output signal indicative of the location of said concealed object.
Claim 2
Independent Claim
178 words
A system for locating a concealed object comprising: transmitting means for transmitting an electromagnetic signal from said concealed object; and receiving and processing means for receiving and processing said electromagnetic signal, said receiving and processing means including antenna means for receiving said electromagnetic signal as an analog signal; amplifying means for amplifying said received analog signal; analog-to-digital converter means for converting said amplified analog signal to a digital signal, said analog-to-digital converter means sampling said amplified analog signal at a predetermined frequency; digital filter means for filtering said digital signal, said digital filter means including a two-stage digital filter, the filter characteristics of said first stage of said two-stage digital filter being defined by parameters AO11 and AO12, and the filter characteristics of said second stage of said two-stage digital filter being defined by parameters AO21 and AO22, wherein AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768, wherein q=quality factor, fctr=center frequency, fsmpl=sampling frequency, and x=1 or 2; and processing means for processing said filtered digital signal to provide an output signal indicative of the location of said concealed object.
Claim 3
Dependent Claim
32 words
A system for locating a concealed object according to claim 1 wherein said antenna means comprises a plurality of antennae, and said amplifying means amplifies the signal received by each antenna individually.
Claim 4
Dependent Claim
32 words
A system for locating a concealed object according to claim 2 further comprising selecting means for selecting the amplified signal from any one of said plurality of antennae or a combination thereof.
Claim 5
Dependent Claim
34 words
A system for locating a concealed object according to claim 1 wherein said locating system further comprises audio means for accepting said output signal and giving an audible indication of the information contained therein.
Claim 6
Dependent Claim
27 words
A system for locating a concealed object according to claim 4 wherein said each of the stages of said two-stage digital filter is a second-order digital filter.
Claim 7
Dependent Claim
28 words
A system for locating a concealed object according to claim 1 wherein said analog-to-digital converter samples said amplified analog signal at a frequency of 78,125 samples per second.
Claim 8
Dependent Claim
29 words
A system for locating a concealed object according to claim 1 wherein said locating system further comprises display means for accepting said output signal and displaying information contained therein.
Claim 9
Dependent Claim
22 words
A system for locating a concealed object according to claim 4 wherein said information comprises the strength of said received electromagnetic signal.
Claim 10
Dependent Claim
28 words
A system for locating a concealed object according to claim 1 wherein said locating system includes input means for controlling said processing means and said digital filter means.
Claim 11
Dependent Claim
18 words
A system for locating a concealed object according to claim 9 wherein said input means includes a keyboard.
Claim 12
Dependent Claim
30 words
A system for locating a concealed object according to claim 1 wherein said transmitting means transmits said electromagnetic signal at a frequency of 1,170 Hz, 8,010 Hz or 29,430 Hz.
Claim 13
Independent Claim
141 words
A method of selecting a two-stage digital filter for use in a locating system including means for receiving a signal radiated from a concealed object as an analog signal, means for amplifying the received analog signal, means for converting the amplified analog signal to a digital signal, and a two-stage digital filter for filtering said digital signal, the means for converting said amplified analog signal to a digital signal sampling the amplified analog signal at a predetermined frequency, wherein the characteristics of said two-stage digital filter are defined by coefficients AO11, AO12, AO21 and AO22, the method comprising: calculating said coefficients AO11, AO12, AO21 and AO22 according to the following formulae: AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768 wherein q=quality factor fctr=center frequency fsmpl=sampling frequency, and x=1 or 2; and performing a stabilization analysis of the digital filter defined by said coefficients.
Claim 14
Independent Claim
141 words
A method of selecting a two-stage digital filter for use in a locating system including means for receiving a signal radiated from a concealed object as an analog signal, means for amplifying the received analog signal, means for converting the amplified analog signal to a digital signal, and a two-stage digital filter for filtering said digital signal, the means for converting said amplified analog signal to a digital signal sampling the amplified analog signal at a predetermined frequency, wherein the characteristics of said two-stage digital filter are defined by coefficients AO11, AO12, AO21 and AO22, the method comprising: calculating said coefficients AO11, AO12, AO21 and AO22 according to the following formulae: AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768 wherein q=quality factor fctr=center frequency fsmpl=sampling frequency, and x=1 or 2; and performing a stabilization analysis of the digital filter defined by said coefficients.
Claim 15
Dependent Claim
37 words
A method of selecting a two-stage digital filter according to claim 12 wherein said step of performing a stabilization analysis of the digital filter defined by said coefficients comprises plotting the impulse response of said digital filter.
Claim 16
Dependent Claim
50 words
A method of selecting a two-stage digital filter according to claim 13 wherein said step of performing a stabilization analysis of said digital filter further comprises examining the plot of the impulse response of said digital filter to determine the length of time required for said digital filter to stabilize.
Claim 17
Dependent Claim
46 words
A method of selecting a two-stage digital filter according to claim 14 wherein said step of performing a stabilization analysis of said digital filter further comprises determining whether the length of time required for said digital filter to stabilize is sufficiently short to meet designed requirements.
Claim 18
Dependent Claim
161 words
A receiver for receiving an electromagnetic signal radiated by a concealed object to indicate the location of said concealed object comprising: a. antenna means for receiving said electromagnetic signal as an analog signal; b. amplifying means for amplifying said analog signal; c. analog-to-digital converter means for converting said amplified analog signal to a digital signal, said analog-to-digital converter means sampling said amplified analog signal at a predetermined frequency; d. digital filter means for filtering said digital signal, said digital filter means including a two-stage digital filter, the filter characteristics of the first stage of said two-stage digital filter being defined by parameters AO11 and AO12, and the filter characteristics of the second stage of said two-stage digital filter being defined by parameters AO21 and AO22 wherein AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768, wherein q=quality factor, fctr=center frequency, fsmpl=sampling frequency, and x=1 or 2; and e. processing means for processing said filtered digital signal to indicate the location of said concealed object.
Claim 19
Dependent Claim
161 words
A receiver for receiving an electromagnetic signal radiated by a concealed object to indicate the location of said concealed object comprising: a. antenna means for receiving said electromagnetic signal as an analog signal; b. amplifying means for amplifying said analog signal; c. analog-to-digital converter means for converting said amplified analog signal to a digital signal, said analog-to-digital converter means sampling said amplified analog signal at a predetermined frequency; d. digital filter means for filtering said digital signal, said digital filter means including a two-stage digital filter, the filter characteristics of the first stage of said two-stage digital filter being defined by parameters AO11 and AO12, and the filter characteristics of the second stage of said two-stage digital filter being defined by parameters AO21 and AO22 wherein AOx1=2*(1-1/q) *cos (2*pi*fctr/fsmpl)*16384 and AOx2=-(1-1/q).sup.2 *32768, wherein q=quality factor, fctr=center frequency, fsmpl=sampling frequency, and x=1 or 2; and e. processing means for processing said filtered digital signal to indicate the location of said concealed object.
Claim 20
Dependent Claim
27 words
A receiver according to claim 16 wherein said antenna means comprises a plurality of antennae, and said amplifying means amplifies the signal received by each antenna individually.
Claim 21
Dependent Claim
27 words
A receiver according to claim 17 further comprising selecting means for selecting the amplified signal from any one of said plurality of antennae or a combination thereof.
Claim 22
Dependent Claim
22 words
A receiver according to claim 16 wherein said each of the stages of said two-stage digital filter is a second-order digital filter.
Claim 23
Dependent Claim
24 words
A receiver according to claim 16 wherein said analog-to-digital converting means samples said amplified analog signal at a frequency of 78,125 samples per second.
Claim 24
Dependent Claim
22 words
A receiver according to claim 16 wherein said processing means provides an output signal indicative of the location of the concealed object.
Claim 25
Dependent Claim
24 words
A receiver according to claim 21 wherein said receiver further comprises display means for accepting said output signal and displaying the information contained therein.
Claim 26
Dependent Claim
17 words
A receiver according to claim 22 wherein said information comprises the strength of the received electromagnetic signal.
Claim 27
Dependent Claim
28 words
A receiver according to claim 21 wherein said receiver further comprises audio means for accepting said output signal and providing an audible indication of the information contained therein.
Claim 28
Dependent Claim
17 words
A receiver according to claim 24 wherein said information comprises the strength of the received electromagnetic signal.
Claim 29
Dependent Claim
22 words
A receiver according to claim 16 wherein said receiver includes input means for controlling said processing means and said digital filter means.
Claim 30
Dependent Claim
13 words
A receiver according to claim 26 wherein said input means includes a keyboard.
References Cited (Backward Citations)
US2601248A
Cited
US3906504A
Cited
US3900878A
Cited
US3975735A
Cited
US4119908A
Cited
US4039938A
Cited
US4070625A
Cited
US4295095A
Cited
US4227405A
Cited
US4438389A
Cited
US4427942A
Cited
US4491785A
Cited
US4642556A
Cited
US4710708A
Cited
US4691165A
Cited
US4709213A
Cited
US4639674A
Cited
US4542344A
Cited
US4600356A
Cited
US4652861A
Cited
US4843324A
Cited
US4806869A
Cited
EP0246886A1
Cited
EP0262882A2
Cited
US4881083A
Cited
US4800385A
Cited
US4837489A
Cited
DE3836219A1
Cited
US4896117A
Cited
GB2221621A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-11-11 | 1995-05-13 | 1995-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-11-11 | 1999-05-13 | 1999-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-11-11 | 2003-05-13 | 2003-11-12 | $7700.00 | Window Closed / Lapsed |